This invention relates generally to medical imaging systems and, more particularly, to methods and apparatus for performing automatic body-contouring imaging.
Diagnostic nuclear imaging is used to study radionuclide distribution in a subject, such as a human patient. Typically, one or more radiopharmaceuticals or radioisotopes are injected into the subject. Gamma camera detector heads, typically including a collimator, are placed adjacent to a surface of the subject to monitor and record emitted radiation. At least some known gamma camera detector heads are rotated around the subject to monitor the emitted radiation from a plurality of directions. The monitored radiation data from the plurality of directions is reconstructed into a three dimensional image representation of the radiopharmaceutical distribution within the subject.
Generally, the resolution of a gamma camera degrades with increasing distance between the imaged area/organ and the detector. Therefore, it is desirable to place the gamma camera as close as possible to the patient to facilitate minimizing the loss of resolution. At least some known imaging systems use non-circular orbits, such as oval or elliptical orbits to facilitate maintaining the detectors position close to the patient during a scan. However, a standard elliptical or oval shaped orbit may not follow the body contour of a patient as closely as possible.
When the imaging system is configured for example, with a pair of gamma cameras in an “L” mode (e.g., for SPECT imaging) as is done when imaging the heart, and other organs, the gamma cameras are configured so the cameras essentially touch one another along adjacent edges. Typical gamma cameras may comprise a large scintillation crystal of NaI optically coupled to an array of Photo-Multiplying Tubes (PMTs). Signals from the array of PMTs are processed to yield the location of the scintillation event on the crystal in what is known as an “Anger” camera. Because of this construction, the gamma camera is less responsive near an outer periphery of the detector. Further, in the “L” mode with fixed gamma cameras, the number of degrees of freedom of movement are reduced. The gamma cameras move only in a lateral motion, which may not follow the body contour of a patient as closely as possible and result in a degradation of image resolution. Thus, only one of the cameras may be positioned at an optimal or preferred distance from the patient while the other camera is positioned at a greater distance that may degrade image resolution.